Secured chips are mostly used in manufacturing of smart cards, security modules, identification devices and other integrated circuits used in applications requiring a high security level.
A secured access to a device or to a distant unit may be authorized by using preferably a one time password introduced on a user terminal unit in response to a challenge sent by the device or the distant unit. For example, document WO2005125078 describes a method for securely communicating between a central location and at least one client station, comprising the steps of: generating an initial secret and storing the same in the central location; generating a set of one-time passwords, each of the one-time passwords being associated with an index; storing a subset of the set of one time passwords in the client station; sending a challenge to the client station from the central location, wherein said challenge is an index of said subset of the set of one- time passwords; sending from the client station to the central location the one-time password associated with the index.
Document EP1392052 describes methods for controlling access to device functions including the steps of receiving a request to enable the feature of the device; determining whether the feature is disabled; determining whether the feature can be enabled with authorization; determining whether a requestor is authorized to enable the feature of the device. When all the conditions are fulfilled by the device and the requestor the feature can be enabled. The authorization may be obtained by generating a challenge value by the device, storing the challenge value, sending the challenge value to the requestor, encrypting the challenge value by the requestor, sending the encrypted challenge value back to the device, decrypting the encrypted challenge value by the device, and comparing the stored challenge value with the decrypted challenge value. If the two values of the challenge are equal, the authorization for enabling the feature is given.
The document EP1441313 handles on an asymmetrical cryptographic method of protecting a hard-wired electronic logic chip against fraud in transactions between the electronic chip and an application including calculating an authentication value from input parameters in the electronic chip. The method comprises the steps of: producing by the chip a random number specific to the transaction; sending to the application a first parameter calculated by the application prior to the transaction, linked to the random number by a mathematical relationship, and stored in a data memory of the chip; calculating by the chip a second parameter constituting an authentication value by means of a serial function whose input parameters are at least the random number specific to the transaction and a private key belonging to an asymmetrical key pair; sending the authentication value to the application, and verifying said authentication value by means of a verification function whose input parameters consist exclusively of public parameters including at least the public key.
The document EP1983466 describes method and apparatus of secure authentication for system on a chip (SoC). The SoC may enable authentication of an external entity attempting to gain access to a function or system. The SoC and an authorized external entity may each have knowledge of hidden data prior to an authentication attempt and may communicate data during the authentication process as well. Using like data, the SoC and external entity may be able to generate the same password and achieve system access. Passwords may be unique in two ways, for example: per operation and per SoC device. A random number generator on board the SoC may enable the passwords to vary for each iteration of the authentication process. Each instance of a SoC has its own secret word allowing passwords to be unique for each device.
The security of the access authentication methods of the prior art may be compromised either by reverse engineering or tampering the keys of the protected chip or by listening or tapping communication between the accessing device and the chip. In fact, several known attacks such as brute force attacks, signal analysis, physical examination of the chip, etc. allow discovering encryption keys and deducing the challenges or other parameters used for creating the one time passwords. In some other cases, the device authentication process creates data sets transmitted from the device to the chip and vice-versa which may disclose important security parameters when captured and analyzed by a third party device.